Submission #403040

#	Time	Username	Problem	Language	Result	Execution time	Memory
403040		Newtech66	Race (IOI11_race)	C++17	0 / 100	4 ms	5792 KiB

race

#include "race.h"
#include<bits/stdc++.h>
#define MAXN 200005
using namespace std;
vector<vector<pair<int,int> > > g(MAXN);
vector<int> subsz(MAXN);
bitset<MAXN> del;
int ans=INT_MAX;
 
void findsubsz(int u,int p=-1)
{
    subsz[u]=1;
    for(auto ch:g[u])
    {
        if(ch.first!=p && !del.test(ch.first))
        {
            findsubsz(ch.first,u);
            subsz[u]+=subsz[ch.first];
        }
    }
}

void solve(int u,map<int,set<pair<int,int> > > &m,int len,int dep,int K,int z=-1,int p=-1)
{
    for(auto ch:g[u])
    {
        if(ch.first!=p && !del.test(ch.first))
        {
            if(len+ch.second<=K)
            {
                if(p==-1)   z=ch.first;
                m[len+ch.second].emplace(dep+1,z);
                solve(ch.first,m,len+ch.second,dep+1,K,z,u);
            }
        }
    }
}

int getcen(int u,int sz,int p=-1)
{
    for(auto ch:g[u])
    {
        if(!del.test(ch.first) && ch.first!=p)
        {
            if(2*subsz[ch.first]>sz)
            {
                return getcen(ch.first,sz,u);
            }
        }
    }
    return u;
}
 
void cendcmp(int u,const int& K)
{
    //cout<<u<<endl;
    findsubsz(u);
    int C=getcen(u,subsz[u]);
    //cout<<"Centroid found "<<C<<endl;
    map<int,set<pair<int,int> > > m;
    solve(C,m,0,0,K);
    /*for(auto p:m)
    {
        cout<<p.first<<": ";
        for(auto e:p.second)
        {
            cout<<"("<<e.first<<","<<e.second<<") ";
        }
        cout<<endl;
    }*/
    if(m.find(K)!=m.end())  ans=min(ans,m[K].begin()->first);
    for(auto p:m)
    {
        int len=p.first,nm=p.second.begin()->first,ch=p.second.begin()->second;
        if(m.find(K-len)!=m.end())
        {
            if(m[K-len].begin()->second!=ch)
            {
                ans=min(ans,nm+m[K-len].begin()->first);
            }else
            {
                if(m[K-len].size()==2)
                {
                    ans=min(ans,nm+(++m[K-len].begin())->first);
                }
            }
        }
    }
    del.flip(C);
    for(auto ch:g[C])
    {
        if(!del.test(ch.first))
        {
            cendcmp(ch.first,K);
        }
    }
}
 
int best_path(int N, int K, int H[][2], int L[])
{
    for(int i=0;i<N-1;i++)
    {
        int u=H[i][0],v=H[i][1];
        g[u].emplace_back(v,L[i]);
        g[v].emplace_back(u,L[i]);
    }
    cendcmp(0,K);
    if(ans==INT_MAX)  return -1;
    else  return ans;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57